• The Journal of Advanced Prosthodontics
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• 제9권4호
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• pp.302-307
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• 2017

PURPOSE. This study compared the SCGAs measured in three types of radiographic images (panoramic, CBCT panoramic-section, and CBCT cross-section images) with values measured using the protrusive occlusal record. MATERIALS AND METHODS. SCGAs were measured in 20 patients on a semi-adjustable articulator using the protrusive interocclusal record. Panoramic and CBCT images were obtained. SCGAs were measured on CBCT images in panoramic and cross sections. In all of the radiographic images, SCGAs were measured using the Frankfort horizontal reference line and the mean curvature line. The most-superior and most-inferior points of the curvatures were identified to determine the mean curvature line. Each measurement was performed twice by two operators independently. The data were analyzed by the t-test, Pearson's correlation test, and Cronbach's ${\alpha}$ using SPSS (${\alpha}=.05$). RESULTS. The mean right and left SCGAs were as follows: protrusive occlusal record (30.1 and 30.2 degrees, respectively), panoramic (38.9 and 38.7 degrees), CBCT panoramic sections (35.4 and 36.8 degrees), and CBCT cross sections (35.3 and 36.1 degrees). The SCGAs differed significantly among the groups. The Pearson coefficients for the correlations with the protrusive occlusal record measurements on the left and right sides were as follows: panoramic (0.834 and 0.791, respectively), CBCT panoramic-section (0.918 and 0.837), and CBCT cross-section (0.918 and 0.845) images. CONCLUSION. Strong correlations were found between SCGAs obtained using radiographic images and the protrusive occlusal record.

• 대한치과교정학회지
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• 제22권1호
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• pp.229-239
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• 1992

This study was performed to define the adaptation patterns of each skeletal components to the flexures of cranial bases, using 91 males from the ages of 17 to 36 and 64 females from the ages of 16 to 34, without orthodontic or prosthetic treatment experiences and with pleasant profiles as subjects. The conclusions are as follow: 1. When considering the changes of flexure of cranial base (Ba-SE-FMN) in both sexes, changes in the anterior cranial base angle to the PM Vertical line (SE-FMN/PMV) were greater than the changes in the posterior cranial base angle to the PM Vertical line (Ba-SE/PMV). Subsequently the nasomaxillary complex showed antero-superior rotating effect as the cranial base angles were increased and postero-inferior rotating effect as they were decreased. 2. Horizontal mandibular angle (Ba-SE-Me) was increased in both sexes as cranial base angle increases (Ba-SE-FMN) and it decreased as the latter was decreases. There by indicating compensatory effects. 3. Maxillary angle (SE-FMN-A) was decreased in both sexes as cranial base angle (Ba-SE-FMN) increases and it increased as the latter was decreased. There by indicating compensatory effects. 4. Mandibular ramus angle to posterior cranial base was decreased in both sexes as cranial base angle increases. There by indicating compensatory effect to anteriorly displaced maxilla and the mandibular ramus angle was increased as the cranial base angle decreases. There by indicating compensatory effect to posteriorly displace maxilla. 5. The length of posterior upper facial height was decreased in both sexes as the cranial base angle increases and it increased as the latter was decreased.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제43권4호
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• pp.256-261
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• 2017

Objectives: The concept of natural head position (NHP) was first introduced by Broca in 1862, and was described as a person's stable physiologic position "when a man is standing and his visual axis is horizontal." NHP has been used routinely for clinical examination; however, a patient's head position is random during cone-beam computed tomography (CBCT) acquisition. To solve this problem, we developed an accelerometer to record patients' NHP and reproduce them for CBCT images. In this study, we also tested the accuracy and reproducibility of our accelerometer. Materials and Methods: A total of 15 subjects participated in this study. We invented an accelerometer that measured acceleration on three axes and that could record roll and pitch calculations. Recorded roll and pitch data for each NHP were applied to a reoriented virtual image using three-dimensional (3D) imaging software. The data between the 3D models and the clinical photos were statistically analyzed side by side. Paired t-tests were used to statistically analyze the measurements. Results: The average difference in the angles between the clinical photograph and the 3D model was $0.04^{\circ}$ for roll and $0.29^{\circ}$ for pitch. The paired t-tests for the roll data (P=0.781) and the pitch data (P=0.169) showed no significant difference between the clinical photographs and the 3D model (P>0.05). Conclusion: By overcoming the limitations of previous NHP-recording techniques, our new method can accurately record patient NHP in a time-efficient manner. Our method can also accurately transfer the NHP to a 3D virtual model.

• 한국멀티미디어학회논문지
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• 제13권3호
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• pp.410-416
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• 2010

본 논문은 광각 렌즈를 가지는 CCD 카메라에서 왜곡 보정 시 필요한 샘플화소의 좌표들을 자동으로 추출하는 알고리즘을 제안한다. 제안한 방법은 광각 렌즈를 통하여 획득한 왜곡된 영상에 대하여 노이즈를 제거한 후 에지 영상을 구한다. 그 후, 수평 방향과 수직 방향에 대한 히스토그램을 임계치와 비교하여 왜곡 좌표를 추출한다. 이 방법은 광각 CCD 카메라의 출력물에 직접 적용 할 수 있다. 그 결과 제안한 방법은 수작업으로 인한 번거로운 작업과 부정확한 샘플 좌표로 인한 오류 없이 자동으로 샘플 좌표를 추출하고 보정한 결과 영상을 얻을 수 있었다. 또한 렌즈 각과 왜곡 형태에 상관없이 적용 가능함을 확인할 수 있었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.340-340
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• 2011

자연하천의 안정은 하상경사, 유사이동, 원지반의 상태, 저수로의 깊이, 하도 및 하안의 구조와 하안식생 등에 달려있다. 이 중 하상경사는 가장 중요한 요소로써 하도의 안정을 위해서는 무엇보다도 이를 적절하게 유지하는 방안을 모색하여야 한다(김혜주 등, 2003). 이러한 자연하천의 안정을 위하여 주로 하상유지시설을 설치하는 것이 보편적이다. 이러한 낙차공의 설치는 하천설계기준을 근거로 하상의 안정성 확보라는 설치 목적에 맞게 설계 및 시공이 이루어져 하도의 안정에는 나름대로 효과적이지만 하천환경의 연속성 차단 등 다양한 생태·환경적 폐해가 나타나고 있는 것으로 알려져 있다(김혜주 등, 2003). 이러한 단점을 보완하기 위해 낙차공과 같은 횡단구조물의 본체에 어도를 설치하거나 계단형 또는 경사형 본체를 갖는 구조물이 제안되고 있으나 현재까지 제안된 보완적인 방법들로는 근본적인 생태단절을 해소하기에는 무리가 있다. 따라서 낙차공 등 하천 수공구조물 설치로 인해 야기되는 생태 환경적 문제를 해결하기 위해서는 대상하천에 서식하는 생물에 대한 이해가 우선 이루어져야 하며 이를 바탕으로 설계 및 시공하는 것이 가장 효과적이다. 이를 위해서는 구조물 설치에 따라 변화되는 수리현상에 대한 정확한 분석이 필요하다. 이에 본 연구에서는 국내외에서 제안되고 있는 낙차공 중 통나무를 이용한 낙차공의 평면형태에 따른 하류부 세굴현상을 수리실험을 통해 분석하였다. 본 연구에서는 평면형태(horizontal)에 따른 세굴영향을 파악하고자 평면각을 $70^{\circ}$에서 최대 $180^{\circ}$로 변화시켜 세굴 실험을 수행하였다. 상향 V형만을 고려한 이유는 하향 V형의 경우($\theta$>$180^{\circ}$)에는 낙차공을 월류하는 흐름으로 인해 구조물 하류부 좌 우안측에 세굴이 발생하기 쉽기 때문에 자연하천의 경우 호안측 침식이 발생한 수 있고 또한 실험수로 벽면영향으로 인해 세굴형태가 왜곡될 우려가 있어 하향 형태의 낙차공은 실험대상에서 제외하였다. 낙차공의 평면 형태가 세굴심에 미치는 영향을 검토한 결과, 유입 Froude 수( )에 대해 높은 상관이 있으며 또한 평면각도에 따라 변하는 낙차공의 횡단길이가 낙차공 하류부의 세굴심에 큰 영향을 미치고 있음을 확인할 수 있었고, 세굴길이의 경우, 평면형태에 따른 세굴길이와 세굴심의 비는 낙차공의 평면각도의 증가에 따라 세굴 길이가 짧아짐을 확인할 수 있었다.

• 터널과지하공간
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• 제11권1호
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• pp.72-78
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• 2001

평면 이방성 암석의 시추 코아를 이용하여 일회의 단축압축시험만으로 이방성 탄성계수를 구하는 방법이 김호영에 의하여 제시되었으나 실험을 통하여 검정한 결과, 한 방향의 포아송비 v$_2$만을 사용하여 탄성계수를 구하는 방법에 문제가 있음이 발견되었다. 본 연구에서는 두 가지의 포아송비, v$_{12}$와 v$_{21}$을 사용하여 이방성 탄성계수를 계산하는 식을 유도하였고, 이방성의 각이 30$^{\circ}$와 65$^{\circ}$인 2개의 시편에 대하여 이방성 탄성계수를 측정하였다. 이방성 탄성계수는 이방성의 각에 따라 다른 식을 사용하여야 되며, 이방성 각이 45$^{\circ}$이하인 경우 v$_{21}$을, 이방성 각이 45$^{\circ}$이상인 경우에는 v$_{12}$를 이용하여 탄성계수를 계산하여야 할 것으로 사료된다.

• 한국운동역학회지
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• 제26권1호
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• pp.71-82
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• 2016

Objective: The purpose of this study was to investigate kinematic comparisons of Tsukahara vault in gymnastics between a top-level athlete and sublevel collegiate athletes in order to obtain information on key biomechanical points for successful Tsukahara vaults. Methods: An Olympic gold medalist (height, 160 cm; weight, 52 kg; age, 25 years) and five sublevel collegiate gymnasts (height, $168.2{\pm}3.4cm$; weight, $59.6{\pm}3.1kg$; age, $23.2{\pm}1.6years$) participated in this study. They repeatedly performed Tsukahara vaults including one somersault. Fourteen motion-capturing cameras were used to collect the trajectories of 26 body markers during Tsukahara vaults. Event time, displacement and velocity of the center of mass, joint angles, the distance between the two hands on the horse, and averaged horizontal and vertical impact forces were calculated and compared. Results: The top-level athlete showed a larger range of motion (ROM) of the hip and knee joints compared to sublevel collegiate athletes during board contact. During horse contact, the top-level athlete had a narrow distance between the two hands with extended elbows and shoulders in order to produce a strong blocking force from the horse with a shorter contact time. At the moment of horse take-off, reactive hip extension of the top-level athlete enhanced propulsive take-off velocity and hip posture during post-flight phase. Conclusion: Even though a high velocity of the center of mass is important, the posture and interactive action during horse contact is crucial to post-flight performance and the advanced performance of Tsukahara vaults.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권4호
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• pp.1368-1389
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• 2014

Three-dimensional multiple-input multiple-output (3D MIMO) and large-scale MIMO are two promising technologies for upcoming high data rate wireless communications, since the inter-user interference can be reduced by exploiting antenna vertical gain and degree of freedom, respectively. In this paper, we derive the achievable sum rate of 3D MIMO systems employing zero-forcing (ZF) receivers, accounting for log-normal shadowing fading, path-loss and antenna gain. In particular, we consider the prevalent log-normal model and propose a novel closed-form lower bound on the achievable sum rate exploiting elevation features. Using the lower bound as a starting point, we pursue the "large-system" analysis and derive a closed-form expression when the number of antennas grows large for fixed average transmit power and fixed total transmit power schemes. We further model a high-building with several floors. Due to the floor height, different floors correspond to different elevation angles. Therefore, the asymptotic achievable sum rate performances for each floor and the whole building considering the elevation features are analyzed and the effects of tilt angle and user distribution for both horizontal and vertical dimensions are discussed. Finally, the relationship between the achievable sum rate and the number of users is investigated and the optimal number of users to maximize the sum rate performance is determined.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.91-98
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• 1999

This paper describes the air flow characteristics inside the throttle valve. Tow-dimensional steady incompressible Navier-Strokes equation are solved numerically with embedding the conceopt of the artificial compressibility and adopting the Baldwin-Lomax turbulence model. With varying the valve opening angles(the Reynolds number )such as 15$^{\circ}$(5000) , 45$^{\circ}$(3000) , 75$^{\circ}$(7000) and 90$^{\circ}$(10000), respectively. tow cases, with a valve shaft and without one, are analysed. The pressure loss between the entrance and exit is severe at 15$^{\circ}$, 100 times as larger as that of 90$^{\circ}$ case, which also depends much on the existece of the valve shaft. The counter rotating vortices are formed over the valve plate with the shaft at only 75$^{\circ}$. They are smally and very large scale in front and back of the valve shaft , respectively. The velocity profiles of 15$^{\circ}$ and 90$^{\circ}$ at the exit are almost symmetric to the horizontal center line, however, the symmetricity is no longer maintained at 45$^{\circ}$ and 75$^{\circ}$ , and in addition, the flow at 75$^{\circ}$ is enforced a lot below center line. The pressure distribution on the walls is largely changed near the valve shaft, and its magnitude becomes great as the valve angle decreases.

• 대한가정학회지
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• 제30권3호
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• pp.15-32
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• 1992

The purpose of this study was to detect the effect of the lower body type on the shape of flare skirts. The subjects for the wearing test were 50 female students, who were controlled in their hip and waist shapes. The skirts used for wearing test were six types(three flar angles $\times$ two fabric types). The effect of lower body type on the shape of flare skirts was determind by the hemline trace method and the silhouette photography. The data were then analyzed by the repeated measures of analysis of variance and the SNK multiple range test. The results obtained from this study were as follows : 1) When a flare skirt made with larger flare angle and better drapable fabric was worn, the numeric of the nodes increased as the drop value(hip - waist) increased. When a flare skirt made with smaller flare angle was worn, the width of horizontal sectio of hemline increased as the drop value increased. The hemline uneveness decreased on the sides and back as the drop value increased. When a flare skirt made with worse drapable fabric was worn, the sides angle of the flarskirt increased as the drop value increased. 2) When a flare skirt made with larger flare angle was worn, the numeric of nodes increased as the ratio of dropped hip increased. The wave-height increased and the back variation ratio of wave-height was higher than the front variation ratio of wave-height as the ratio of dropped hip increased. The hemiline uneveness decreased on the back as the ratio of dropped hip increased. When a flare skirt made with larger flare angle was worn, the sides angle of the flare skirt increased as the ratio of dropped hip increased.